The present embodiments relate generally to fluid-gauging assemblies and methods, and more particularly to fluid-gauging assemblies and methods for determining properties of fuel used in a gas turbine engine.
In one exemplary application, a gas turbine engine can be used on an aircraft. In aircraft engine control, it can be necessary to know a value of a mass flow of fuel due to mass flow's direct effect on engine thrust. Prior fuel gauging techniques have obtained fuel mass flow values using moving components within the engine. For example, two impellers connected by a shaft with a known spring constant have been used to find fuel mass flow given the proportional relation between torque on the shaft (and thus impeller angular displacement) and fuel mass flow. However, fuel-gauging techniques which utilize moving components are undesirable.
Fuel mass flow is equal to the product of fuel volumetric flow and fuel density. Fuel volumetric flow is readily obtained using known techniques. Thus, an accurate measurement of fuel density can yield fuel mass flow. Prior fuel gauging techniques have attempted to accurately determine fuel density by either directly measuring fuel density in a fuel tank external to the engine using some form of a densitometer, or measuring a dielectric constant of the fuel in the fuel tank external to the engine and then deducing fuel density using this measured dielectric constant in the fuel tank. However, such techniques do not provide an accurate enough measurement of fuel density to allow for precise, economical aircraft engine control.